1. Field of the Invention
The present invention is related to vehicle barrier systems, and more particularly to net-based vehicle barrier systems that span a long distance that can be readily raised or lowered and that can be easily deployed.
2. Description of Related Art
Originally, net-based barrier systems with energy absorption devices at end supports were associated with aircraft arresting devices. These systems are designed so that the aircraft arresting net system is let out more than 100 feet upon impact and the aircraft slowly decelerates to a stop over a long distance, to minimize damage to the aircraft. Such systems are not directly applicable to vehicle barrier systems because the net system, energy absorption units, and end supports of vehicle barrier systems are designed to completely stop vehicle over a short distance regardless of the amount of damage caused to the vehicle.
Vehicle barrier systems rated to stop a 15,000 lb vehicle at impact speed of 50 mph of the prior art include large sliding steel gates, steel bollards filled with concrete and anchored into footings, interlocking concrete surface barriers, horizontal steel bars with end supports, pop up steel plates, steel cable systems at short spans with fixed end supports, and other related barrier systems of the prior art. These barrier systems are limited by the length of area that can be secured without adding fixed supports that penetrate the subsurface, and this limitation is typically 15 to 60 feet. In addition, these barrier systems require an electrical power supply, require backup power systems, and use hydraulics or pistons, resulting in maintenance, repairs, and downtime of the barrier. Many of these systems are not an “all weather” use. These barrier systems are either semi-fixed in-place and are not easily removed, or permanently fixed in-place and, therefore, permanently block off vehicle access to the secured area. Onsite installation of prior art systems can take several weeks. System components are neither modular nor disconnected easily. Barriers made of steel and concrete create additional projectiles upon an impact event, and require significant repair work in the aftermath to restore a barrier to operational status.